Python programmers may be familiar with Python's yield keyword and generator functions. Python has built-in language support specifically for generator functions, whereas PLT Scheme does not. Can we invent our own then?

Ruby Garden has an entry on IterationStyles that has a comparison between Ruby and Python, which makes an interesting reference. I've classified this one under DataStructureRecipes until we can come up with a better place. Maybe there should be a whole chapter on how to emulate idioms from other programming languages?